Lubricant



United States Patent 3,265,617 LUBRICANT Charles M. Allen, Columbus,Ohio, assignor, by mesne assignments, to The Battelle DevelopmentCorporation, Columbus, Ohio, a corporation of Delaware No Drawing.Continuation of application Ser. No. 172,802, Feb. 12, 1962. Thisapplication Feb. 5, 1965, Ser. No. 430,735

1 Claim. (Cl. 252-25) The present application is a continuation ofearlier copending application Serial No. 172,802, filed February 12,1962, now abandoned.

This invention relates to a new lubricant and lubrication method. Moreparticularly, it relates to a lubricant and a method for substantiallyreducing the coefficient of friction between rubbing, contactingsurfaces over a wide temperature range by using as a lubricant a mixtureof metal-free phthalocyanine and molybdenum disulfide.

At the present time, there is no lubricant available that will maintainthe coefficient of. friction between two rubbing, contacting surfaces ata low value over a wide temperature range. For example, there are manylubricants that provide adequate lubrication between contacting surfacesat temperatures below 600 F. When the temperature goes much beyond 600F., these lubricants break down and galling between the surfaces occurs.On the other hand, lubricants effective at a temperature above 600 F..are generally inefiective at lower temperatures.

Today, however, there are many applications or situations where surfacesare in rubbing contact over temperature ranges of 90 F. to 1500 F., andabove. Supersonic space flights usually encounter such conditions. Thus,there is a need in the art for a lubricant and a lubrication method thatwould prevent excessive wear and galling of rubbing, contacting surfacesover the temperature range of 90 F. to 1500 F.

It is an object of this invention to provide a lubricant that wouldmaintain a low coefficient of friction between rubbing surfaces over atemperature range of from -90 F. to 1500 F.

It is another object of this invention to reduce the coefl'icient offriction between rubbing, contacting surfaces over the temperature rangeof from 90 F. to 1500 F. by lubricating with a mixture of metal-freephthalocyanine and molybdenum disulfide.

It has been known in the art for many years that molybdenum disulfide isan effective lubricant at temperatures up to 500-600 F. Above thistemperature, oxidation of molybdenum disulfide occurs. Metal-freephthalocyanine is utilized as a lubricant over the temperature range of70 to 1350 F. Metal-free phthalocyanine is very effective as a lubricantat from 500-600 F. up to 1200- 1350 F. At temperatures below 500-600 F.the lubricating ability of metal-free phthalocyanine is diminished.

It has been discovered that when a mixture of metalfree phthalocyanineand molybdenum disulfide is used as a lubricant to reduce thecoefficient of friction and wear between contacting surfaces, a lowercoefficient of friction results over a wider temperature range than isobtained with either constituent singly. This behavior cannot beanticipated or predicted from the known properties of the individualconstitutents of the mixture. Themetalfree-phthalocyanine-molybdenum-disulfide mixture was found to havelubricating properties over the temperature range of from F. to 1350 F.superior to either metal-free phthalocyanine or molybdenum disulfidealone at any given temperature over that range. Specifically, using thecoefiicient of friction as a yardstick, themetalfree-phthalocyanine-molybdenum-disulfide mixture is a substantiallybetter lubricant than (1) molybdenum disulfide alone, at temperaturesbelow 600 F., and (2) metal-free phthalocyanine alone, at temperaturesabove 600 F. As has been pointed out, this result is entirelyunexpected.

This invention comprises a lubricant comprising a mixture of metal-freephthalocyanine and molybdenum disulfide and a method comprising applyingsuch lubricant to surfaces in rubbing, contacting relationship.

The coefii-cient of friction observed between contacting surfaces is notsensitive to the ratio of the constituents of themetal-free-phthalocyanine and molybdenum-disulfide mixture. A mixture ofabout 30 percent by weight of metal-free phthalocyanine is satisfactoryfor use throughout the entire temperature range of from 70 F. to 1350 F.In general, high percentages of metal-free phthalocyanine are desirableat higher temperatures. At temperatures above 600 F., metal-freephthalocyanine should comprise 50 percent or greater by weight of themixture, and at temperatures below 500600 F., less than 50 percent byWeight of the mixture. At temperatures above 600 F., when air or oxygenis present, metal-free phthalocyanine should preferably comprise greaterthan percent by weight of the lubricant mixture. Air or oxygen can beexcluded from the lubrication site at these elevated temperatures by useof an artificial atmosphere, such as nitrogen. With a nonoxidizingatmosphere present, more nearly equal weights of phthalocyanine andmolybdenum disulfide form an effective lubricant mixture.

There is no critical method for preparing the mixture of metal-freephthalocyanine and molybdenum disulfide. Dry powdered metal-freephthalocyanine and dry powdered molybdenum disulfide are mixed togetherby conventional means in the desired proportions. After mixing has beenaccomplished, a portion of the mixture is placed between the rubbing,contacting surf-aces, with provision for a reserve supply of thelubricant mixture, so that some of the mixture is always maintainedbetween the rubbing surfaces. Again, conventional techniques for addingsolid lubricants may be employed in adding the lubricant mixture of thisinvention.

The lubricant is eifective whether the rubbing, contacting surfaces aremade of metal or nonmetals, or mixtures thereof. The lubricant has beenfound to be particularly effective in lubricating bearing surfaces.Thus, the lubricant described herein is not only highly effective over awide temperature range but is also effective for a broad spectrum ofmaterials that may be in rubbing contact.

It is again pointed out that the lubricant comprising a mixture ofmetal-free phthalocyanine and molybdenum disulfide is most effective inlubricating bearings under operating conditions. Since, at the point ofrubbing contact, 'bearings operate at high temperatures and pressures,harsh conditions are imposed onany lubricant used in this application.The high degree of effectiveness of the method and lubricant describedherein under such extreme conditions clearly illustrate their greatvalue, as well as their versatility.

The following examples are intended to be illustrative of the manner inwhich the metal-free-phthalocyanine (PCH )-molybdenum disulfide (M08mixture is employed as a lubricant in specific applications:

Example I Dry powdered metal-free phthalocyanine and molybdenumdisulfide were blended fifty-fifty by volume and thoroughly mixed. Thismixture was applied as a lu- 4 Example 11 at 40 pounds, which isequivalent to about 100,000 p.s.i.

maximum Hertz contact stress, if no wear has occurred. The followingdata applied to this run:

Average lube flow Amplitude of Disk temper- Operating gmJmin. Averagevariation of Wear track ature, F. time, coefficient friction width, mm.minutes of friction coefficient (M08 (P CH2) 1 Average over entire run.

bricant between two disks in rubbing contact with one another, saiddisks having the following composition.

Material: Percentage by weight Nickel 2.5 Chromium 32.0 Tungsten 17.0Iron 3.0 Carbon 2.5 Others 2.5 Cobalt Balance The coefficient offriction was then measured as the 4 temperature was varied over therange from 130 F. to

The conditions of Example II were repeated, utilizing a new set of disksof the same composition as those of Example II, and the following datawere obtained:

Average lube flow Amplitude of Disk temper- Operating gm./m1n. Averagevariation of Wear track ature, F. time. coefijcient friction width, mm.minutes of friction coefficient (MoSz) (P CH 1200 F. A nitrogen carrierwas used to supply lubricant between the rubbing surfaces. The maximumflow rate of the nitrogen carrier was 1 cubic foot per minute. A load ofpounds was applied. A load of 40 pounds corresponds to about 100,000p.s.i. maximum Hertz stress. The running time at maximum load was 32minutes, and the total running time was 36 minutes. The averagecoeificient of friction at maximum load was 0.03 to 0.09. Afteroperation under these conditions, the disks were examined and showedsmoothed high spots in roughened high-temperature track and a polishedlow-temperature track. The disks were contacted at 9400 feet per minuterolling speed, with 4 percent sliding.

Previous operation under these conditions with other lubricants hadcaused damage to the high-temperature wear track. Included in theseother lubricants were metalfree 'phthalocyanine and molybdenum disulfideas individual lubri ants.

After operation, the disk surfaces exhibited a continuous film, with noscoring or pitting. The addition of some metal-free phthalocyanine, tomolybdenum disulfide was intended to reduce the rather high friction ofmolybdenum disulfide, particularly in the 800 F. to 1000 F. temperaturerange, and to reduce lubricant build-up tendency at elevatedtemperatures. The combination was unusually effective, giving very lowwear, low friction (lower than either constituent alone), and smoothoperation throughout the temperature range from room temperature up to1200 F. Lubricant build-up after high-temperature operation was verylow. While there was some build-up during low-temperature operation,brief periods at high temperature were sufficient to drive olf theexcess lubricant, leaving only thin, smooth films. There was no scoringor pitting.

Example IV The materials and load conditions of Example II wererepeated, utilizing an air environment. In this run, dry nitrogen wasnot used as a lubricant carrier and environment. In this airenvironment, the following data were phthalocyanine begins to slowlydecompose at a temperaobtained: ture of 900 F. The rate of decompositionremains essentially constant until a temperature of about 1150 F.

Average lube flow Amplitude of Disk temper- Operating gm./1n1n. Averagevariation 01 Wear track ature, F. time, coeilicient friction width, mm.minutes of friction ooeflieient The disk wear surfaces were smooth andwere similar in is reached. At temperatures above 1150, the rate isappearance. 5 increased but not catastrophically. One of the decompo-Example V sition products is hydrogen and the hydrogen evolution tendsto blanket the lubrication site, thereby excluding DlSkS of the samecomposition as those of Example II oxygen. and contacted under the sameconditions were lubricated Likewi e, since the mixture effectivelylubricates at only with molybdenum disulfide. Under these conditions, 20room temperature, it is expected that it would serve the following datawere obtained: effectively as a lubricant down to 90 F., and below.

0 perating Average Average Amplitude Disk 'Iempertime, lube flow,coefficient of variation Wear track ature, F. minutes gmjmin. offriction of friction width, mm.

coefficient 15 .5 15 .04 2 7 5 .4 10 .03 5 .4 .03 5 .4 13 .02 5 .4 13.02 These data reveal that when molybdenum disulfide While the examplesdeal with metal compositions, the f used as lllbflcant, the averageCoefliciellt 0f metal-free-phthalocyanine-molybdenum-disulfide mixturefrlctlofl 1S Poorer y afactor of at least t e t will also effectivelylubricate cermets, ceramics, and{Hetal-ffee'Phtha}?Wanna-{molybdenum-d1$111fide mlXtlfre plastics. Whilethe examples describe a method of solid- 1s used. In add1t1 on,the d1sksurfaces were covered with l bri a t l b i ti n by mean of a carriergas, other myfladsof y fine P mechanisms are quite possible. Theseinclude bonded Example VI solid lubricant films in which bonding agentis any one The materials and the conditions of Example II were of anumber of Organic resins metal matficesagain repeated, using metal-freephthalocyanine alone as aerospace applications, Sticks Of Gold Pressedlubricant a lubri a t, The pertinent d ta were; powders 1n contact withthe surface are anticipated. Also,

Operating Average Average Amplitude Disk Tempertime, lube flow.coefficient of variation Wear track ature, F. minutes gun/min. offriction of friction width, mm.

coefiicient Based on theaverage coefiicient of friction, metal-freelubricant transport by evaporation (vapor phase) is conphthalocyaninealone is poorer by a factor of at least 2, sidered to be a goodpossibility in the vacuum of outer and under some conditions by a factorof 3, than a lubri- Space. The vapor pressure of the individuallubricant cant mixture of metal-free phthalocyanine andmolybconstituents, molybdenum disulfide and metal-free phthaldenumdisulfide. ocyanine, are attractive for such potential applications.

Example VII What is claimed is:

A lubricant composition for lubricating contacting metal-containingsurfaces in an oxidizing atmosphere wherein said metal-containingsurfaces are at a temperature in the range from about 70 F. to about1350 F. consisting essentially of a mixture of metal-free phthalocyanineand molybdenum disulfide, wherein the concentration of metal-freephthalocyanine is in the range of from about 5 to about 95 percent byweight.

If titanium-carbide cermet disks were lubricated in separate experimentswith (1) a mixture of metal-free phthalocyanine and molybdenumdisulfide, (2) metal-free phthalocyanine alone, and (3) molybdenumdisulfide alone, coeificients of friction measured over a widetemperature range would be substantially lower where the mixture ofmetal-free phthalocyanine and molybdenum disulfide was used as thelubricant.

In some experiments the lubricants were evaluated at References Cited byf Examiner 1350 F. Experiments did not go beyond a temperature of 1350F., because of limitations of the furnace equip- Fundamental Processes111 Lubl'lcatll'lg Metal Surfaces ment. Since the mixture waseffectively serving as a at 100 to 1700 F., by E- N- Klemgard inLubricatlubricant at 1350 F. and the rate of decomposition of 111gEnglneeflng, October 1960, P g metal-free phthalocyanine above 1350 F.,although in- 68-476- creasing rapidly does not preclude its use, thereis every l reason to expect that this lubricant mixture would be DANIELWYMAN P 1mm y Exammer' effective at significantly higher temperatures.Metal-free IRVING VAUGHN, Assistant Examiner.

